Someone already mentioned the excellent GamuT DI-150---very nice and quite expensive.
Another really good integrated is the Linar 10--and not nearly as expensive as the DI-150. It is a 5.1 channel integrated that can be switched into four channels into two-channel stereo for the easiest bi-amping I know. (Its a matter of connecting speaker cables appropriately and hitting a switch on the remote.) I heard this unit (at a friends house) played as a normal stereo amp and liked it a lot, then heard it in 4 x 2 stereo, bi-amped, and it blew my sox off. Four channels of clean, 125 watts (each) in stereo mode really sang.
Linar gear sounds clear, open, extended, musical, and controlled. The frequency extension is the first thing I noticed: lows go quite low and the highs seem to just go on and on. It is on my short list if I want to down size.